页岩卸荷流变力学特性的试验研究

EXPERIMENTAL STUDY ON RHEOLOGICAL MECHANICAL PROPERTIES OF SHALE UNDER UNLOADING CONDITION

岩体开挖卸荷产生的变形具有时间效应,其瞬时力学及流变力学响应都会有一定的变化。当前,对此流变行为的研究多建立在加载力学基础上的岩石流变试验,而未考虑岩石卸荷应力路径下的流变特性,往往与实际力学过程不相吻合。选取乌江彭水水电站地下厂房新鲜页岩进行恒轴压、逐级卸围压应力路径下的卸荷流变试验,对岩石的三轴卸荷流变特性进行初探。试验表明,页岩在较低应力水平下,轴向及侧向蠕变曲线呈现出衰减阶段的流变特性。基于试验成果,对H-K三元件模型参数进行非线性回归,从而得到页岩在该应力状态下的卸荷流变本构方程。研究表明,该模型能很好地描述该应力路径下页岩的卸荷流变行为。

The deformation of rock mass takes on time-dependent effect after its excavation;and the instaneous mechanical and rheological mechanical responses of rock mass vary greatly in some degree. At present,the research on this rheological behaviour is mostly based on loading conceptual rock rheological test. However,researches on the rheological property under unloading stress path are seldom taken into account. Thus,the results sometimes cannot coincide with the practical mechanical process. The fresh shale sample in underground powerhouse of Pengshui Hydropower Station are taken to carry out unloading rheological test under the stress conditions of constant axial stress and gradually unloading lateral stress so as to preliminarily study its triaxial unloading rheological property. Experimental research reveals that the axial and lateral creep curves of shale specimens behave the attenuation creep stage under relatively low stress state. The rheological constitutive equation is obtained by means of parameters regression of H-K three-component model. Research reveals that the H-K three-component model can well present the unloading rheological behaviour under this stress state.